1. Field of the Invention
The invention relates to a control apparatus and a control method of a vehicle, that controls at least one of the driving force and the braking force of a vehicle and a vehicular control method.
2. Description of the Related Art
Among known transmissions disposed between a driving force source and a drive wheel of a vehicle, there is a stepwise variable transmission that shifts the speed ratio by controlling the states of engagement and disengagement of engagement devices such as a synchromesh mechanism, a friction engagement device, etc. A vehicle having a friction type clutch or an electromagnetic clutch between a stepwise variable transmission and a driving force source performs a control of reducing the torque transfer power of the clutch at the time of a speed shift. Reduction in the torque transfer power of the clutch at the time of a speed shift reduces the torque transferred from the driving force source to a drive wheel. As a result, the accelerating performance of the vehicle drops, incurring the possibility of discomforting an occupant in the vehicle.
Furthermore, if a speed shift is performed and the torque transfer power of the clutch is reduced while the vehicle is coasting with a generally-termed engine brake force caused by transfer of kinetic energy from wheels to the driving force source, the engine brake force temporarily weakens at the time of the speed shift, incurring the possibility of discomforting a vehicle occupant. Vehicular control apparatuses capable of avoiding the aforementioned drawbacks are known. For example, Japanese Patent Application Laid-Open Publication No. 2000-308206 describes such a vehicular control apparatus.
A vehicle described in this patent application is designed so that power of an engine is transferred to driving wheels via a transmission and a drive shaft. A motor-generator is connected to the drive shaft. The motor-generator is driven by supplying it with electric power from a battery, and torque of the motor-generator is transferred to the driving wheels via the drive shaft. The transmission installed in this vehicle is a stepwise variable transmission equipped with a synchromesh mechanism. By switching the synchromesh mechanism, the transmission achieves speed shifts.
At the time of a speed shift operation of the transmission involving the discontinuation of transfer of torque from the engine to the drive wheels, the drop in acceleration can be reduced by transferring torque of the motor-generator to the driving wheels. At the time of a speed shift of the transmission during a coasting run of the vehicle, the drop in the braking force that acts on the vehicle can be reduced by increasing the regenerative brake force of the motor-generator.
The motor-generator as described in the aforementioned patent application undergoes changes in the outputtable torque or regenerative torque depending on various conditions, such as the temperature of the motor-generator, the temperature of the battery, the state of charge of the battery, the voltage of the battery, etc. Therefore, depending on these conditions, the motor-generator becomes unable to generate a target regenerative torque or a target output torque needed for a speed shift of the transmission. Hence, there exits a possibility that a speed shift may change the braking force or the driving force, and therefore may discomfort a vehicle occupant.